Various display systems are known for aircraft simulator applications used to train pilots and other aircraft crew members. The simulators allow training in a ground-based facility and attempt to provide simulated experiences and situations which are as close to actual events as possible. One of the drawbacks of present simulator systems is the limited field of view (FOV). The FOV is often insufficient to provide vision in the areas necessary for multiple training tasks, such as landing training and refueling training. These tasks in particular require the largest possible FOV display.
Preferred simulator systems today use an off-axis backscreen/mirror visual display system (OABD) for providing a large field of view display for the pilots and other crew members. The OABD systems use projectors which project an image onto a backscreen member which in turn redirects the image beam onto a collimating mirror. The mirror in turn redirects the beam to the observer's eyepoint.
The vertical FOV of OABD systems is normally limited since the portion of the backscreen that displays the lower portion of the FOV also blocks or occults the observers' upper FOV. Attempts to increase the FOV coverage in the downward direction have adversely affected (that is, decreased) the FOV coverage in the upward direction. Similarly, increases in the upward FOV coverage have decreased the FOV coverage in the downward direction.
Some attempts to overcome these limitations in current OABD system designs have moved the eyepoint of the observer forward and/or downward with respect to the display. Similarly, some systems have instead moved the display in a backward and/or upward direction with respect to the observer's eyepoint. These allow the downward FOV coverage of the backscreen to be increased; however the upward FOV coverage again becomes partially occulted by the backscreen. Moreover, moving the eyepoint or display thusly degrades the collimation (convergence and divergence) and/or distortion characteristics of the OABD system. This in turn can lead to significant problems with eyestrain or the ability to use the system.
It is an object of the present invention to provide an improved OABD system for use in aircraft simulator applications. It is another object of the present invention to provide an improved OABD system with an increased vertical field of view.
It is another object of the present invention to provide an OABD system with an increased vertical field of view which does not decrease the field of view in other directions or areas. It is still further object of the present invention to provide an improved OABD system which increases the field of view but does not degrade the collimation and/or distortion characteristics of the display.